With the widespread use of mobile technologies, the mobile terminal is becoming one of the everyday commodities in modern life. Recently, the mobile terminals have evolved to be multimedia communication devices supporting various data transmission and supplementary services as well as traditional voice communication service.
Recent mobile terminals support multimedia functions such as still/motion picture recoding function, image view function, voice recoding function, audio playback function, and document view function such that the user can create and save contents with these functions. As it becomes common to share data, diverse data sharing techniques are developed for the users to share various types of data such as document and still and motion pictures.
As data sharing techniques are diversified and used in various fields, it becomes more and more important to secure the private information and business secrets of companies. Recently, it is common to share the secret documents such as business contracts, internal recordings of business, and private conference records by means of mobile terminals and thus the loss of the mobile terminal or illegal public opening of the documents stored in the mobile terminal can cause significant security problems.